1. Field of the Invention
The present invention relates to a sheet discharge tray, and more particularly to a sheet discharge tray that stacks sheets such as originals, printing paper, or plastic sheets discharged from a sheet conveying apparatus that conveys sheets and is provided in an image forming apparatus, such as a copying machine or a printer, an image reading apparatus, such as a sheet feed scanner, etc., as well as a sheet conveying apparatus, a image forming apparatus, and an image reading apparatus having the sheet discharge tray.
2. Description of the Related Art
A sheet conveying apparatus that conveys sheets is provided in an image forming apparatus, such as a copying machine or a printer, and an image reading apparatus, such as a sheet feed scanner. This kind of sheet conveying apparatus discharges conveyed sheets onto the stacking surface of a sheet discharge tray provided in the image forming apparatus or the image reading apparatus. Some sheet discharge trays are provided with an extension tray, described later using FIG. 9, in order to stack large size sheets that are discharged from the sheet conveying apparatus (for example, see Japanese Laid-Open Patent Publication (Kokai) No. 2004-010220 (FIG. 2)).
FIG. 9 is a side view showing schematic configuration of a conventional sheet discharge tray.
In FIG. 9, a sheet discharge tray 10 comprises a plate-shaped member 11 on which a stacking surface 11a is formed for stacking sheets discharged from sheet discharge section 20 of a sheet conveying apparatus, an extension tray 12 comprising a plate-shaped member, on which an extension stacking surface 12a is formed, that is capable of face-to-face superposition with the stacking surface 11a, and a pivot 13 that is provided between the plate-shaped member 11 and the extension tray 12. The pivot 13 is provided in proximity to the end of the stacking surface 11a in the discharging direction. The plate-shaped member 11 rotatably supports the extension tray 12 via the pivot 13.
The extension tray 12 arrives at a housing position (not shown) by being rotated in the direction of an arrow D shown in FIG. 9. At the housing position, the extension stacking surface 12a of the extension tray 12 is opposite to the stacking surface 11a of the plate-shaped member 11. When the extension tray 12 is in the housing position, a sheet of a size that is smaller than the length in the discharging direction of the stacking surface 11a, such as a business card or a postcard, can be stacked on the surface opposite to the extension stacking surface 12a of the extension tray 12, i.e. the rear surface. In contrast, when stacking sheets that are longer than the length in the discharging direction of the stacking surface 11a, the extension tray 12 is rotated in the opposite direction to the arrow D to reach the extension position shown in FIG. 9.
According to the sheet discharge tray 10 shown in FIG. 9, the length of the stacking surface of the sheet discharge tray 10 can be changed depending on the size of the sheets to be discharged from the sheet discharge section 20 of the sheet conveying apparatus.
As described later using FIG. 10, a sheet discharge tray that stacks sheets discharged from a sheet conveying apparatus while aligning the sheets has also been proposed (for example, see Japanese Laid-Open Patent Publication (Kokai) No. 10-109807 (FIG. 1)).
FIG. 10 is a side view showing schematic configuration of another conventional sheet conveying apparatus in which a sheet discharge section is provided.
A sheet discharge tray 30 that is connected to a sheet conveying apparatus 300 as shown in FIG. 10 comprises a base 31 on which are formed a sloping surface 31a and a horizontal surface 31b for stacking sheets discharged from sheet discharge section 320 of the sheet conveying apparatus 300, a first end fence 32 provided at the end in the discharging direction of the base 31, two ribs 35 that are vertically arranged in parallel in the discharging direction on the upper surface of the base 31, and a second end fence 33 as a abutment plate that is provided between the two ribs 35. The second end fence 33 may also be configured to be movable in the discharging direction.
According to the sheet discharge tray 30 shown in FIG. 10, since the sloping surface 31a is formed to become lower as it proceeds towards the end side in the discharging direction, through the force of gravity, the sheets can be stacked so as to collide against either the end fence 32 or the end fence 33 depending on the sheet size. It is therefore possible to reduce misalignment among the discharged sheets in the discharging direction.
Further, in a case where the size of the discharged sheets is small, since the inside faces of the ribs 35 contact the sheets before the sheets collide against the end fence 33, the ribs 35 can function as widthwise regulating plates that reduce misalignment among sheets with regard to the width direction that is orthogonal to the discharging direction.
According to the sheet discharge tray 10 shown in FIG. 9, an improvement in the discharging direction alignment of sheets can be expected by forming a sloping surface in which the stacking surface 11a and the extension stacking surface 12a become lower as they approach the sheet discharge section 20. However, an improvement in the alignment of sheets in the width direction that is orthogonal to the discharging direction can not be expected. It is thus necessary for the user to remove a bundle of sheets that is stacked on the sheet discharge tray 10 and correct the misalignment in the width direction.
Further, according to the sheet discharge tray 30 shown in FIG. 10, an improvement in the discharging direction alignment of discharged sheets can be expected when the user adjust the position in the discharging direction of the second end fence 33 to match the size of discharged sheets. However it is necessary for the user to consume time to adjust the position of the second end fence 33. Furthermore, according to the sheet discharge tray 30 shown in FIG. 10, since a sheet whose width exceeds the space between the two ribs 35 is stacked on the upper surface of the ribs 35, an improvement in the width direction alignment of such sheets can not be expected. Therefore, when large size sheets are discharged, the user must perform the time consuming work of removing a bundle of sheets that are stacked in a disorderly manner on the sheet discharge tray 30 and then aligning the bundle of sheets.